The Specific Origin of Slow Inhibition in the Brain

Inhibitory processes play an important role in information processing in the cerebral cortex. The origin of a particular subtype of these processes, slow cortical synaptic events mediated by γ-aminobutyric acid type B (GABAB) receptors, is not clear. Are they initiated by specific presynaptic cells, or can they be activated by high-frequency action potentials in most interneurons? Tamás et al. show that GABA release at synapses between GABAergic neurogliaform interneurons and pyramidal cells in layers 2 to 3 led to the combined postsynaptic activation of GABAA and GABAB receptors. This finding indicates that slow, GABAB-mediated inhibitory postsynaptic potentials arrive from unitary sources in cortical networks.